Bus-bar



April 9, 1957 J. A. MATHEWS ET AL 2,788,420 BUS-BAR Filed Nov. 4, 1954 United States atent BUS-BAR Joseph A. Mathews, Barrington, and Howard 'H. Mann, Chicago, Ill., assiguors, by mesneassignments, to;Chi-. cago. Musical Instrument Company, Chicago, 111., a corporation of Illinois Application November 4, 1954, Serial No. 466,738

Claims. (Cl. 200-466) This invention relates to circuit making and. breaking mechanism of the class. primarily, but not necessarily designed, intended and adapted for use in electrical networks employing a nus-bar from which low voltage signals impressed thereon from a tone signal generating system are adapted to be transmitted from said system to a signal translating system in response to circuit making engagement of key controlled contactors with said bus-bar.

The herein disclosed exemplified embodiment of our invention has for itsprimary purpose the provision of an organization of electrically coactive elements including (a) a unique type of bus-bar and, preferably but not necessarily, use in association therewith of (b) an equally unique type or preferred type of resilient contactor; the forms, shapes and designs of these elements being such and so calculated that when the contactor engage said busbar, multiple points of surface contact are provided between said elements to thereby greatly contribute to the general effectiveness of the invention as a means for selectively transmitting current of low voltage and low amperage to a work circuit.

A further important object of the invention is the provision of an arrangement of electrically coactive circuit making and breaking elements for use primarily in the keying circuits of what have come to be known as electric organs embodying playing-key controlled contactors for selectively impressing the outputs of tone generators upon a bus-bar for conduction of saidoutputs to an electroacoustic translating system, the arrangement, forms, shapes and designs of 'the elements being such that but a slight amount of key pressure is required to insure perfect electrical engagement of the contactors with the bus-bar, and whereby the effective points of surface contact between the contactors and said bus-bar are self-cleaning and selfpolishing by their rubbing action against each other.

A still. further object is the provision of a bus-bar characterized by a substantially uniformly rough surface as distinguished from the uniformly smooth surface of a conventional bus-bar such as a straight length of drawn, wirelike conductive material of circular cross section and uniform diameter throughout, the roughness of surface being predetermined to provide sensibly identical, longitudinally disposed, immediately adjoining pairs of effective contact surfaces in which each pair of said surfaces is coactive with a respective key operated contactor when the latter is in circuit-completing engagement therewith.

A still further object is the provision of a contactor which is resilient and consists of closely related wound portions of springy conductive wire, which contactor'is adapted to be tangentially related to the bus-bar and to engage longitudinally spaced apart contact surfaces of a respective pair of such surfaces on the bus-bar and to be flexed so as to invite and cause a plurality of the windings of the wire to yieldingly engage said surfaces, thereby adding further to the actual number of effective points of surface engagement between the contactor and said contact surfaces.

Theabove-mentioned and other features and advantages of the herein disclosed invention and the manner of attaining them will become more apparent by reference to the following description in conjunition with -the-accompanying drawings, wherein:

Figure 1 is a view in elevation of which the bus-bar is formed;

Figure 2 is an illustration of two different profiles of the thread-like portions on the surface of the manufactured product;

Figure 3 is a plan view showing the construction and relationship to each other of the thread-like portions on the finished bus-bar;

Figure 4 is a view taken longitudinally through a small section of the bus-bar, the relative proportions being. exaggerated;

Figure 5 represents transverse sectional views of the busbar taken substantially on the linesa -a; b-b, and c-c respectively of Figure 4;

Figure 6 is a schematic illustration of the composite organization of electrically coactive elements of the invention; and

Figure 7 is a sectional perspective view of a slightly modified form of our invention.

The perfectly smooth surfaced rectilinear metal stock 10 shown at Figure 1 may be Phosphor bronze, German silver or any well known equivalent metal possessing good electrical properties. Said member is of uniform diameter and of circular cross. section and of any desired length. When used in the herein disclosed environment or in electricalcoaction with a given type of circuit making and reaking contactor, satisfactory results are had when the diameterof the stock is .050 inch. in this connection, however, it is not intended that the invention be limited as regards dimensions, proportions or the precise shapes and forms of the several elements.

For the functional purpose of our invention, the metal stock 10 is converted into a unique form of bus-bar co. prising a rectilinear member A, the exterior of which is rough and characterized by sensibly identical, equidistantly axially spaced apart, circular thread-like portions 11 which are concentric to the long axis of the stock and parallel to each other, such that the finished product has a surface, the outward appearance of which is similar to a fastener formed with an external V-thread. Conversion of the original smooth surfaced stock may be accomplished by; methods commonlyknown in the screw industry. At a inFigure 2 is shown the thread-like shapes of said portions 11, and it is noted that in profile said portions are similar to the American Standard V-thread, the crests 12 being rounded and the roots 13 which adjoin the opposing faces of any two successively related portions 11 being similarly rounded. At b in Figure 2, the crests 11 and the roots 13 are sharp, this being the only difference between the two shapes.

Referring to Figures 3, 4 and 5 of the accompanying drawings, Figure 3 shows a small length of the formed product there being in the instant example fifty of said portions 11 per inch. As the profile of each portion 11 is similar to the profile of the American Standard V- thread, certain of the terms employed to define the shapes, forms, dimensions, diameters and pitch of a V-thread the metal stock from fastener are employed herein to describe said portions, reference being taken to the following specifications:

Normal diameter of the stock taken onv transverse -nular thread-like portions 11.

Thus, the formed article is quite like that of the surface of a conventional fastener having an external V- thread. The article is circular in cross section at all places in its length, as illustrated at Figure 5. As the circular thread-like portions 11 are equidistantly spaced apart so as to follow one another in unbroken succession axially of the article, the outwardly flared sides and 16' of any two successive related ones of said portions mutually define an annular groove 14 between each pair of said portions, which groove is V-shaped in a plane axially of the article. Stress is placed upon the configuration of this groove and the manner in which it is defined by said outwardly flared sides 15' and 16 as this is an important feature of our invention when the formed article is employed in electrical coaction with a cross-sec tionally circular resilient contactor which we will now describe in detail.

An organization of electrically coactive elements is illustrated at Figure 6, the same comprising two similar bus-bars l6 and 17, the former connected to ground 18. From bus-bar 17 is a conductor 19 adapted to be connected to the input circuit of the power amplifier of an electroacoustic translating system (not shown). The busbars are mounted on a support 28 of dielectric material and, as illustrated, said bus bars are disposed in spaced apart parallel relation. Mounted on said support 2% and extending from one side thereof and through the space between said bus-bars is a resilient cross-sectionally circular contactor 21. It is noted that the space between said bus-bars is sufficiently in excess of the diameter of said contactor so that the latter is free to he flexed from a position of engagement of same with bus-bar 16 to a position of disengagement thereof with bus-bar 17.

No claim is made for means for activating said contactor 21 except in the herein disclosed environment. At

Figure 6- is a vertically movable motion transferring element 22. having a hole 23 passing horizontally therethrough for freely accommodating the free end of said contactor. Retractile spring 24 normally urges element '22 to the downward limit of its vertical movement, the

upper end of said element 22 being freely hung from the back end of a playing-key 25 which has pivotal motion about a horizontal axis. Consequently, said contactor is resiliently urged against bus-bar 15. When the front end of key 25 is depressed, contactor 21 moves off of bus-bar l6 and onto bus-bar 17. A signal conductor 26 from a signal supply source (not shown) is connected to the opposite end of contactor 21. When contactor 21 is engaged with bus-bar 17, signal voltage will be impressed thereon for conduction to the aforementioned signal translating system.

The contactor is formed from a single length of spring wire and its windings are substantially in abutting relationship so that, in effect, the contactor is a cross-sectionally circular structure throughout its length. Thus it is capable of fiexure in a vertical plane so that it is electrically coactive with said bus-bars in the manner aforestated. At point X the diameter of the contactor is approximately .050 inch and, as shown. at Y in Figure 2, same is adapted to partly enter a respective V-shaped space 14 where it has rubbing action against the oppositely related angular faces of an adjoining pair of said an- By reason of the stated nice-ties of shapes, forms and sizes of the coating elements and the relationship of the elements. there is provided a multiplicity of effective contact surfaces between the contactor and said bus-bars. During vertical flexure of the contactor, adjacent wound portions of the wire spread slightly and rub against the angular faces of said adjoining portions 11., thereby further increasing the surface of contact and at the same time and by rubbing engagement with said faces maintaining a clean and more or less polished condition of said faces and the windings of the coil that engage same.

To the best of our knowledge a bus-bar, the surface of which is rough as distinguished from smooth surfaced busbars of the prior art, is broadly new and never before has been known to or used by any other person. We therefore claim this feature per so as well as in combination with a contactor, the latter coacting with the former to provide a multiplicity of effective contact surfaces between these elements.

At Figure 7 is shown a solid bar of metal, one surface of which is formed with a longitudinal row of equidistantly related portions 26 capable of functioning substantially in the manner of the thread-like portions 11 in the preferred embodiment of the invention.

While we prefer to use a resilient contactor comprising a closely wound coil of springy wire, we wish it understood that straight lengths or single strands of Phosphor bronze, German silver or other well known cross-sectionally circular wire can be used with excellent results. The functional difference between these various types of contactors is that a contactor comprising a closely wound coil requires only slight pressure of the coil against the bus-bar with resultant slight relative spreading of adjacent windings of the coil. The greater thenumber of windings that engage the flared faces of a respective groove 14, the higher is the efficiency of the device because of the increase in the number of effective surfaces of contact between the bus-bar and the contactor. At no time will the effective points of surface contact be less than three or four. It is understood that the pressure required to engage the contactor with the bus-bar is no greater than that required to depress a playing-key, the same generally being from about two to two-and-a-half ounces. It is also understood that the diameter of the coil where it engages the bus-bar is such relative to the greatest dimensional size of groove 14 as not to cause the contactor to become wedged between the opposite faces of said groove. 1t suffices to say that the coil has perfect freedom of angular motion in both its circuit making and circuit breaking movements.

We have disclosed two embodiments of the invention, in each of which the surface construction of the metal stock, when viewed in section in the axial plane of the stock, is of hill-and-dale configuration as defined by side surfaces having an angle of 45. in each of these examples the exterior of the material is rough as distinguished from the smooth surface of a conventional busbar. In the preferred embodiment of the invention in which the finished product is produced from smooth surfaced cross-sectionally circular stock, a section taken in the axial plane of the stock and at any place in the circumference of the material discloses the aforementioned hill-and-dale configuration. Stated differently, the formed material in this preferred embodiment is identical both longitudinally and at all places circumprising a straight length of wire-like conductive material,

the exterior of which is characterized by the regular occurrence thereon of coaxial axially parallel annular grooves which are parallel to each other, and equidistantly related longitudinally of said material.

3. As a new article of manufacture, a bus-bar comprising a straight length of wire-like conductive material, the exterior of which is characterized by the regular occurrence thereon of coaxial annular grooves which are parallel to each other, each of said grooves being of V-shape in the axial plane of said material, and equidistantly related to each other longitudinally of said material.

4. As a new article of manufacture, a bus-bar comprising a rectilinear length of cross-sectionally circular wire-like conductive material, the surface of which has formed thereon equidistantly spaced apart coaxial annular portions, the shapes of which in the axial plane of the material are substantially like the profile of the American Standard V-thread.

5. A bus-bar comprising a longitudinal, cross-sectionally circular member of wire-like conductive material References Cited in the file of this patent UNITED STATES PATENTS 419,487 Wollensak Jan. 14, 1890 1,950,194 Samad Mar. 6, 1934 2,573,895 Evett Nov. 6, 1951 

